Commutator



July 23, 1929. KRQEHLE 1,721,515

' I COMMUTATOR Filed Jan. :50, 1928 Patented July 23, 1929.

UNITED STATES RALPH KROEHLE, O F WARREN OHIO.

COMMUTATOR.

I Application filed January 30,'1928. Serial No. 250,603.

V This invention relates to commuta'tors and to a method of making thesame. It has become highly desirable to use molded commutators forelectric motors, especially motors of the smaller horse power type. Itis essential that such commutators possess high insulating propertiesand will withstand the heat generated in service as well as beingcapable of maintaining their integrity of construction under allconditions of use. Various attempts have been made heretofore in the artto provide molded commutators. using plastic setting materials, butthese have not proved satisfactory, asthey disintegrate under thebursting strain to which the commutators are subjected in service. Inother types of plastic material bodies there is an objectionable featurethat the body is softened under heat permitting the commutator segmentsto become loosened and thus destroy the effectiveness ofv the structure.7

, Objects of my invention are to provide an improved molded commutatorwhereinthe material ofthe body is of a metallic nature; to provide acommutator formed with a body of metal in which the commutator segmentsare secured; and to provide a method of constructing such commutators.

With these and such other objects in view as will be apparent from thedescription, the invention resides in the novel construction,combination, and arrangement of parts as well as the method hereinafterdescribed and claimed and illustrated in the accompanyingdrawingswhereof Figure 1 is an end elevation of a vertical typecommutator as mounted .on an armature shaft. r

" Figure 2 is a vertical section therethrough on the line 22 of Figure1.- 1 Figure -3 is a rear face elevation of one of the commutatorsegments employed.

Figure 4; is an end elevation of a horizontal type commutator as mountedon an armature shaft. 4 v

Figure 5 is a vertical section taken there through. In detail, thevertical'type commutators comprise an annular series of commutatorsegment bars 5, of copper or other-suitable metal, having verticallyplane outer faces for brush contact with the brushes 6 and 7, thesegments being spaced apart by strips. of mica or other suitableinsulating members 8. The body of the commutator to which these segmentsand insulating members are attached in the disclosed embodiment consistsof a molded body 9 of type metal, this material being best adapted forthe purposes of the invention and being the preferred material employedin the formation of the bodies. The rear face of each commutator segmentis formed with an undercut recess 10 for receiving a corresponding head11 eX- tending from the body 9 when the metal is cast into the/recesses,thus providing a rigid connection between the commutator segments andthe body. Interposed between the body 9 and-the rear face ofeachcommutator bar is an insulating shield 12 formed-of any suitablematerial such as asbestos, baked on enamel, or varnish, or any suitableinsulating medium which is applied as a coating-or backing sheet to theinner faces of the commutator segments before the body 9 is'molded orcast in place. Suitable means are provided in the type metal body tionsembedded in the body 16, which is, of

course, formed of molded type metaL In this form of the invention thecontact brushes 16 and 17 engage horizontally against the outer contact'faces of the commutator bars. As in the vertical type, the commutatorsegments 15 are arranged in an annular series being spaced apart byinsulating members, comprising mica strips 18 and the outer contactsurface of each segment is raised slightly above the outer peripheralface of the type metal body 16 as best shown in Figure 5. Each of thecommutator bars 15 is undercut at each end to form a recess and toprovide an anchor head 19 which is material whichis adapted for thepurpose nated. Type lnetal has the peculiar characand may be formed ofasbestos, enamel, or varnish, etc., so long as it. possesses therequisite insulating properties.

In both types of commutator, the insu-. lating members which aredisposed between the series of segments are of co-extensive area withthe segments and are of identical.

configuration so that the segments and insulating strips are positionedside by side to form. uneven surface at their inner faces for receptionof the backing sheet of insulating material 12 or 20 as thc'case may be.This arrangement may be varied as desired.

The method of constructing these commutators is carried out by properlyassenibling the commutator segn'ients and their interposed insulatingstrips in a jig and tightening the same in position. :backing 12, or 20asthe case may be, is then 'applied over the inner faces of the assem-The insulating bled segments and insulating strips, care being taken tosee that it entirely'covers every portion of the commutator segments andinsula ting strips which are to be embedded or in contact with. the bodyof type metal. After this insulating backing has been applied, asuflicientquantity of melted type metal ispoured or cast into the formand in the process of molding the metal will, of course, flow; into therecesses i'ornied by'under-cutt-ingthe inner portions of the respec tivesegment bars, thus filling all the recesses and engaging around-theanchoring tongues whereby When the metal body-1s cooled andhardened,-the COll'ilHllliltOl segments will'be .firmly embedded in thetype metal body.

The fastening element 13, shown in Figure 2, may be positioned inthe atthe time th commutator segments are assembled and before pouring of thetype metal body. 7 The resulting structureproduces an extremely durable,strong, rigid commutator having a body of metal which is capable ofresisting any bursting strain to whici the commutatortmay be subjected.-Any developed heat tends to distribute substantially uniformly over theentire body of thecommutator and the metalfwill not soften. Thecommutator segments are held rigidly in position and any disalignment orrelative dislocation therebetweenis absolutely elimiteristic ofexpanding slightly upon cooling so that the metal is forcedby internalpressure in the molecular structure of the metal itselffinto eil'ectiveengagement'within the recesses formed in the embedded portions of thesegment bars.

In compliance with statute, I have described one complete embodiment asusing type metal, but I may equally well employ any alloy, metal orsuitable material which will fulfill the purposes of the invention.

, WVhile I have illustrated and described in this form of the inventionthe best means I have thus far devised for carrying it into etlect, I(.leire it to be understood that the invention is not limited thereby,but that any desired changes and modifications may be-inade in thestructuraldetail as will fall within the scope of the invention asclaimed.

I claim:

1. A commutator comprising commutator bars embedded in a body of metalmolded thereon and insulated ,theretroni.

2. A commutator comprising metalcommntator bars insulated and embeddedin a body of type metal molded thereovc'r. i "3. A. commutator having amolded body of typemctal; 4.' A commutator comprising connnutator barsspaced apart by insulating members, an insulating backing over said barsand spacing-'n'ienibers, and a body of metal molded .around portions ofsaid bars for anchoring said bars to the body. 5. The method of making acommutator, "which; consists in embedding comn'iutator bars having anapplied insulating material thereon, in a body of molten metal andcooling the metal to'lorm the connnutator. (5. The method of making acon'imutator, which consists in arranging commutator barscircumfcrentially with interposed insulating strips between therespective bars, 'applying an insulating covering over the innerportions of said bars and insulating members, and pouring molten metalinto the interior ofthe assembled structure to form a body-on coolin mALPH; KROEHLE.

